Collaborative Research: The Differential Impact of Parasitic Diseases on Agricultural Productivity of Blacks and Whites in the Early Twentieth-Century South

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This project examines the impact of parasitic diseases on the productivity of populations of different ancestral heritages in the early 20th-century American South. The research has historical significance because it quantifies the relationship between endemic parasitic diseases and the economic well-being of two historically important populations, African-Americans (blacks) and European-Americans (whites). The project helps explain the economic development of the American South and address questions concerning the productivity of 19th-century southern slavery. The research focuses on the geographical distinctiveness of diseases and the differential biological susceptibilities of blacks and whites to particular endemic diseases, primarily to parasitic hookworm and malaria. The research gathers archival data from the Rockefeller Archive Center on the prevalence of parasitic diseases in the early 20th-century for all available counties for eleven southern states. The project uses the available disease prevalence rates with various climatic, geographical, etiological factors, and other disease-related data to estimate (impute) disease prevalence rates for those southern counties that lack explicit disease data. The research employs the explicit and imputed disease prevalence rates along with agricultural input and output data for 968 southern counties to estimate differences in county-level economic productivity (agricultural output) between black and white agricultural labor. The econometric estimations of productivity control for other pertinent variables and correct for various statistical concerns.The broader significance of the project is that it provides data for estimating the impact of parasitic diseases in the world today. The role of endemic hookworm and malaria in explaining early 20th-century economic productivity of southern black and white agricultural labor assists in understanding the economic impact of these diseases today. Hookworm currently infects between 20 and 33 percent of the world's population; malaria infects 300 to 500 million people and kills 2 to 3 million per year. The economic impact of these diseases is not known with much precision, but early 20th-century estimates suggest hookworm reduced labor productivity from 20 to 70 percent. Malaria's economic impact is just now being studied. A hypothetical but plausible estimate for the impact of hookworm alone illustrates the possible magnitude of the costs of these diseases. Using the 20 percent hookworm infection rate means that about 1.2 billion people worldwide are infected. If hookworm infects people with a per capita income equivalent of $800 U. S. dollars (people in the world's poorest nations) and reduces annual productivity just 15 percent, the economic losses due to hookworm alone are $144 billion per year. Capitalized at an interest rate of 4 percent, this represents a permanent wealth reduction of $3.6 trillion for the world's poorest peoples. This calculation is imprecise. But it suggests that throughout much of the developing world the control of endemic parasitic diseases may be an effective way to combat poverty. This project's estimation of the lost economic productivity attributable to hookworm and malaria establishes more precise boundaries for estimating the contemporaneous effects of these diseases.